xxxviii BRITISH FOSSIL CORALS. 



54. Genus Hydnophora. 



Fischer de Waldheim, Descrip. du Mus. Demidoff, vol. iii, p. 295, 1810; Monticularia, Lamarck, Hist, des 



Anim. sans Vert., t. ii, p. 248, 1816. 



Corallum formed of irregular series of corallites, united by their walls, which are thick, 

 compact, and constitute ridges, divided longitudinally, so as to represent rows of conical 

 prominences, or monticula3. The calicular trenches are transversal as well as longitudinal, 

 and there is no columella. Septa nearly equal, and rising to the apex of the conical mural 

 monticulse. General form sometimes massive and sub-globose or gibbous ; sometimes 

 sub-explanate. 



Typ. sp., Hydnophora Demidovii, Fischer, Oryct. du Gouv. de Moscou, pi. xxxii. 



Section III.— ASTREDLE DENDROIDAL. 



Corallum always increasing by lateral gemmation. The corallites segregate, and having 

 an arborescent or fasciculate arrangement. Septa regularly and delicately serrated ; those 

 of the principal cycla always bearing pali. 



55. Genus Cladocora. 



(In parte) Ehrenberg, Corall. des Roth.Meeres, p. 85, 1834; Caryophyllia, Dana, Zoophytes, p. 378, 1846. 



Corallum arborescent, forming branched clumps. Corallites cylindrical, very long, and 

 completely free laterally. Calices circular, or almost so. Columella papillose. Pali well 

 developed, and corresponding to all the septa, except those of the last cyclum. Septa 

 slightly exsert, nearly equal, granulated, and having their apex arched and delicately serrated. 

 Walls compact, with simple, granulated, or echinulated costae, and an incomplete epitheca, 

 which often expands into circular, horizontal leaves, extending to the neighbouring 

 corallites. 



Typ. sp., Cladocora cespitosa, Milne Edw. and J. Haime ; Madrepora Jlexuosa, Solander and Ellis, tab. 

 xxxi, figs. 5, 6. 



56. Genus Pleurocora. 



Milne Edw. and J. Haime, Comptes rend, de l'Ac. des Sc., t. > xvii, p. 494, 1848. 



Corallum sub-dendroid. Corallites cylindrical, very short ; united by their basal part, 

 and free towards their upper end. Columella, pali, and septa much as in the preceding 

 genus. Walls compact, extremely thick, and never presenting any traces of an epitheca. 

 Costa distinct from one end of the corallites to the other, and vermiculate. 



This genus approximates in some degree to Dendrophylha and to Oculina. 



Typ. sp., Pleurocora explanata, Milne Edw. and J. Haime, Ann. des Sc. Nat., 3 me serie, vol. x, 

 tab. vii, fig. 10. 



